Yes, something like that is in the roadmap.

We’ve been scrambling to get things ready enough for this initial launch, but Mike managed to get the Standard Library open sourced this morning: https://github.com/observablehq/notebook-stdlib

One of the next pieces we'd like to open-source is the Notebook Runtime — All of the JS that you need to take a blank webpage, and host a notebook within it.

After that, there's some file format details to figure out — hopefully a notebook can just be published and consumed as a standard ES Module. But then we'll be most of the way there.